The mechanisms of induction of immunologic tolerance to a defined protein and hapten (sheep gamma globulin and the TNP determinant) in T and B cells will be studied in terms of the functional properties of these cells; that is, carrier function (T) and hapten-specific antibody formation (B). Manipulation of the tolerant state in vivo or of tolerant cells in vitro prior to adoptive transfer will be attempted to determine the processes which occur in tolerance induction and how they can be controlled. The metabolic activity of cells from tolerogen-injected animals will be assessed by in vitro culture. Finally, mitogen- unresponsiveness and the role of suppressor cells will be evaluated as models for the tolerance process.